Harry Redknapp writes "like a two-year-old" and is the most "disorganised person in the world", a court heard today.
An interview with the Tottenham Hotspur manager from 2009 was aired on day four of a tax evasion trial.
Both men deny the charges of intent to defraud revenue and customs out of tax and national insurance contributions.
Redknapp, in the 2009 interview, told officers: "I am not going to fiddle taxes, I pay my accountant a fortune to look after me.
"I am completely and utterly disorganised. I write like a two-year-old and I can't spell."
He added: "I'm the most disorganised person in the world. I can't work a computer, don't know how to email. Never sent a fax or even a text message."
The Englishman also said that he rarely takes care of his own finances, telling the court that he wrote a column for The Sun for 18 months and didn't notice that he wasn't getting paid.
"My accountant runs my life. I haven't seen a wage slip for possibly ten years. I don't have bank statements," the 64-year-old continued.
"I pay a fortune to my accountant to look after me. He pays my bills. He runs my life."
Earlier, the Southwark Crown Court heard that Redknapp had sole responsibility for the Monaco bank account, called 'Rosie 47' after his dog and year of birth.
The prosecution alleges that Mandaric made payments totalling $295,000 (£188,000) into the account when he was chairman and Redknapp was manager.
The trial continues.